<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>

    .hide{
        display: none;
    }
    .box:hover .hide{
        display: block;
    }
   
</style>
<body>
    <div class="box">
        <div class="hide">111111111</div>
        <input class="c" type="button" name="" id="" value="显示"><br>
    </div>

</body>
</html>